Bigjedd,

Yes, heard of the same problem up here as well, I have a 416 Ruger, but made up on a P14 action, I haven't personally shot factory ammunition myself, but I have had problems getting any velocity from it, about 2150-2200 fps is about all I can get. I also have a 416 Taylor, and can get better velocities from it, which I suppose speaks something of it's efficiency. I'm assuming the Hornady factory ammunition is loaded to the hilt, with non-canister propellants.
I have just got my copy of the #8 Hornady manual and even Hornady only list 1 load that makes 2350 fps, the majority of loads sit in the 2150-2250 fps range.

The gunsmith that made my rifle has also made a couple of Browning BLR's in 416 Ruger, and I know one of them has had serious pressure problems using factory ammunition, same thing as yours, when he opens the lever, the primers are falling out of the cases. The other rifle has just been handloaded.

I shoot some cast bullets in mine as well, and noticed early on that the throat length seems very short indeed, and I'm starting to wonder if that's no part of the problem.
My gunsmith is ordering a 416 throating reamer, I'm going to get mine taken out a little, mainly for the cast bullets, but I'm going to chronogrpah a few loads before and after to see what, if any difference that makes.

I'm also looking heavily at trying Reloder 17, as it seems to be a good one, but that's according to Quickload.
In any case, a 400 grain bullet at 2150-2200 will pretty much knock anything over I would ever intend shooting with it.

Regards,
David.